The present invention relates generally to an innovative approach to computer-based radar systems, and more particularly to a multi-mode boresight correction process Especially designed for the Air Force""s Airborne Warning and Control System (AWACS).
The boresight correction procedure of the present invention is required for the Air Force""s Airborne Warning and Control System (AWACS). This system uses radar equipment carried on E-3 Sentry aircraft.
The operators of AWACS systems, referred to as xe2x80x9cweapons directorsxe2x80x9d, perform tasks that are similar to those of a flight controller but that are far more complicated. Specifically, a weapons director has the additional responsibility of enhancing the combat capability to the fighter he controls. Not only does he transmit data about aircraft location, direction, and speed, he also communicates command directives, mission modifications, weather updates, airfield closures, refueling information, and coordination between other fighting elements both airborne and on the ground. He must know what information that pilot needs and be able to provide it at the appropriate time. The weapons director must learn to read a two-dimensional radar display, listen to communications from pilots, and from that, recognize what is occurring. In short, a weapons director must attain the knowledge and develop the decision-making abilities required to direct fighters in combat.
To date, AWACS weapons directors have been required to learn these skills in live training or during actual combat missions, but they have found that in a typical scenario, a target is first acquired by a targeting aid such as a ground-based radar or an AWACS aircraft. After the target is identified as potentially hostile, this information and the approximate location and velocity of the target are communicated to the launch aircraft. The targeting information is downloaded into the missile guidance computer, and the missile is launched. The missile then flies in a pattern either directly toward the target or on in a circuitous path so that the target continues to exhibit relative motion. The position and velocity of the target may be periodically updated with messages from the targeting aid to the missile guidance computer in some designs, and there may be no communication with the missile after launch in some other designs. For a successful mission, the sensor of the missile acquires the target during the terminal flight phase and guides the missile to the target. In the terminal phase of the flight, the AWACS targeting radar must be able to identify the target, but elevation boresight (beam pointing) errors have been found on several E-3 antennas after these antennas have been installed in their respective aircraft. In order to correct these errors in the past, it has been necessary to either remove the antenna from its aircraft installation; a very time-consuming process; or retune the antenna aperture phases, on aircraft, aircraft, by using an aperture coupled probe technique, which while very useful at one frequency, is not a practical solution for the reboresighting of an antenna at multiple frequencies because of the complexity of the test and the large amount of time involved in performing the test.
A need exists for the reboresighting of an E-3 antenna at all operating frequencies (typically eight or ten frequencies), in approximately one day or less. This represents a Please change line 10 of page 3 to read:
U.S. Pat. No. 6,053,736 issued to Huffman et al;
U.S. Pat. No. 5,458,041 issued to John Sun;
U.S. Pat. No. 4,825,223 issued to Brian Moore: and
U.S. Pat. No. 3,947,776 issued to Daniel Stevens.
The above-cited systems are useable with AWACS and Joint Stars systems, and are improved by the present invention, as discussed herein.
The present invention is a boresight correction procedure for use on a phased array of radiating elements that steer signals electronically by phased adjustment. The process begins as on an element by element basis, one measures phases between signals at Port A to Port B of the antenna feed network to get a phase measurement angle that corresponds to an angular difference between outgoing radar signals and target echo return signals. Next, the signal processor applies a least squares fit equation to the angular distance to get a correction phase slope across the array xcex40, and applies a phase slope correction of 67 to the phases of the transmitted signal.
It is an object of the invention to provide an automatic boresight correction procedure for radar systems. This and many other objects and advantages of the present invention will be readily apparent to one skilled in the pertinent art from the following detailed description of a preferred embodiment of the invention and the related drawings.